Hard-surfacing process



y 27, 1965 N. J. ZACHMAN 3,196,538

HARD'SURFACING PROCESS Original Filed Nov. 24. 1961 2 Sheets-Sheet 1 I7\wmmnnuullulm ,IllIIIIIIIIIIIIIIIIIIII III!III 51 INVENTOR. NEIL J.ZACHMAN ATTORNEY July 27, 1965 N. J. ZACHMAN 3,196,538

HARD-SURFACING PROCESS Original Filed Nov. 24, 1961 2 Sheets-Sheet 2INVENTOR.

NEIL J.ZACHMAN A 7'TORNE Y United States Patent 3,196,538 HARD-SURFAQHNGPRGCESS Neil J. Zachman, Wiilowdaie, Ontario, Canada, assignor to UnionCarbide Canada Limited, Toronto, Gntarro, (Ianada, a corporation ofCanada Griginai appiication Nov. 24, 1961, Ser. No. 154,690, now PatentNo. 3,159,463, dated Dec. 1, 1964. Divided and this appiieation Nov. 7,1963, Ser. No. 322,182 4. Claims. (Cl. 29-487) This application is adivision of co-pending application Serial No. 154,600 filed November 24,1961, now Patent No. 3,159,463 issued December 1, 1964.

The present invention relates to a method for providing a wear-resistantsurface for steel articles. More particularly, the present inventionrelates to a method for providing steel articles with a wear-resistantsurface formed of wrought cobalt-base alloy material.

In view of the very high degree of resistance of various cobalt-basealloys to abrasion, heat, corrosion, and erosion, there has beenconsiderable effort in the art to provide relatively economical andsimple methods for applying a surface of these materials on the edges ofsteel articles such as chain saw guide-bars and the like.

Various techniques have been proposed which have been directed primarilyto the spraying or melting of cobalt-base alloy material onto thesurface of the article to be hard-surfaced. Additionally, bead-weldingprocesses have been suggested for joining cobalt-base alloy material tosteel articles.

While deposition techniques and bead-welding have been successful invarious applications, it has been found that, for economic and otherreasons, there is a need to provide a more direct and less costly methodfor providing high-strength, wear-resistant surfaces on the edges ofcertain articles, not-ably chain saw guide bars, slitter knives,circular saws, scraper blades, chisels, surgical instruments and thelike.

It is therefore an object of the present invention to provide a simpleand direct method for providing wear-resistant surfaces for steelarticles of the type described.

Other objects will be apparent from the following description and claimstaken in conjunction with the drawing in which:

FIGURE 1 shows, somewhat schematically, a plan view of apparatussuitable for hot-forming strips of wrought cobalt-base alloy for use inthe present invention.

FIGURE 2 shows a sectional side elevation of the arrangement of FIGURE1.

FIGURE 3 shows a plan view of a pre-formed strip of cobalt-base alloyand the steel article to which it is to be joined.

FIGURE 4 shows a plan view of a fixture suitable for hOlding apre-formed strip of cobalt-base alloy material and a steel articleduring operation of the process of the present invention.

FIGURE 5 shows a sectional side-elevation view of the fixtureillustrated in FIGURE 4 together with a tungsten electrode arc-meltingapparatus and FIGURE 6 shows a plan view of a steel chain saw guide-barafter being provided with a wear-resistant surface in accordance withthe present invention.

It has been discovered, as part of the present invention, and contraryto what would be expected by those skilled in the art, that certaincobalt-base alloys, in

arrests Patented July 27, 1365 wrought form, can be effectively joinedto steel articles Without the use of additional metallic bondingmaterial to provide a composite article having a strong wearresistantsurface. The cobalt-base alloys which have been found suitable for thispurpose are those having a composition of between about 30 and 31percent chromium, about 4.5 percent tungsten, between about 1.1 and 1.6percent carbon, up to 1.5 percent molybdenum, up to 3 percent nickel, upto 3 percent iron, up to 2 percent silicon, up to 2 percent manganese,the balance being substantially all cobalt. Alloys of this compositionare readily available commercially in the form of sheet, strip, plateand the like.

A process in accordance with the present invention for providing awear-resistant surface on a steel article comprises arranging wroughtcobalt-base alloy material of the aforesaid composition in closelyadjoining relation with a steel article and fusing the adjoining,opposite portions of the steel article and wrought cobalt-base alloymaterial to form a mass of fused metal therebetween consistingessentially of material derived from the fused portions of thecobalt-base alloy and steel article; subsequently causing the fusedmetal to solidify; and postheating the thus produced composite articleto avoid fracture in the heat-affected zone of the steel portion of thecomposite article.

The above-described process is particularly directed to providingwear-resistant surfaces on the edges of chain saw guide bars and similararticles through the use of wrought cobalt-base alloy strips having athickness of between about inch and 4 inch. Such strips can beconveniently formed by shearing from sheets or plates of commerciallyavailable wrought material.

The present invention will be more fully understood by reference to thedrawing which shows in FIGURES 1 and 2 a strip of cobalt-base alloy 1arranged in a conventional hot-forming apparatus which is adapted toproduce shapes corresponding to the edges of a steel article which is tobe hard-surfaced. The apparatus comprises a female die 3 and a male die5 which is actuated pneumatically or by other convenient means.Cobalt-base alloy strip 1 has a composition in the range previously setforth and is cut from a sheet of wrought material having a thicknesssubstantially equal to the edge of the steel article which is to behard-surfaced.

When installed in the hot-forming apparatus, the strip is mounted oninsulator 7 and heated to between about 18GO F. and 2200 F. by means ofelectric current supplied by direct current source 9 through conductors11 and 13. Gther suitable techniques such as induction heating can alsobe used to pro-heat the cobalt-base alloy strip.

After being suitably pro-heated, the strip is hot-formed by virtue ofthe force exerted by male die 5 after which it is removed from thehot-forming apparatus. The thus produced pre-formed wrought strip isindicated as 15 in FIGURE 3 where it is shown with a plain carbon steelchain saw guide-bar 17 with which it is to be joined for the purpose ofproviding a wear-resistant surface.

The pro-formed strip and the steel chain saw guidebar are arranged inclosely adjoining relation by means of a suitable fixture indicatedgenerally as 19 in FIG- URES 4 and 5.

With reference to FIGURES 4 and 5, fixture 19 is seen to comprise -asteel support member 21 and steel 3,19e,5as

. 3 V V holding members 23 and 25. The steel article to behard-surfaced, i.e. guide-bar 17, is located in fixture 19 as shown,together with the pre-formed Wroughtstrip of cobalt-base alloy 15.Guide-bar 17 and cobalt-base alloy strip 15 are held in place by meansof clamps 27 and 29. Additionally, a replaceable copper .back-up '31 isarranged beneath the adjoining portions of guidebar 17 and cobalt-basealloy strip 15.

FIGURE additionally shows a tungsten electrode 33 which forms part of an'arc melting' apparatus indicated generally as 35. Theiheat provided bythe electrode is used to fuse the adjoining and opposite portions ofguidebar 17'and'cobalt-base alloy 15.

When the pre-formed wrought cobalt-base alloy strip and plain carbonsteel guide-bar 17 have been arranged in closely adjoining relation asillustrated in FIGURES 4 and 5, the adjoining port-ions of the wroughtcobalt-base alloy strip 15 and guide-bar 17. are fused by means totungsten electrode 33 to provide a mass of fused metal between the alloystrip and the guide-bar. This mass of fused metal is indicated as 37 inFIGURE 5 and consists essentially of material derived from the steelguide-bar and cobalt-alloy strip. V The aforementioned fusion operationis accomplished so that the portion of the cobalt-base alloy stripremote from the steel guide bar remains un-melted and substantially inas wrought condition- Heliarc type arc-melting apparatus employing atungsten electrode having no filler rod is preferred for fusing theadjoining portions of the wrought strip and steel guide-bar althoughother techniques such as short-arc, metal-arc, and resistance fusionprocesses can be employed in many applications of the present invention.

, The fusion and subsequent solidification ofthe adjoin- 7 ing portionsof strip 15 and guide-bar 17 produces a composite article having an edgewhich is formed of wrought cobalt-base alloy. r V In order to preventcracking in the steel base member of the thus produced compositearticle, post-heating is required after solidification of the fusedmetal which can be accomplished in accordance with those known techniques which are commonly applied in the'production of bead-welded steelarticles, With plain-carbon steel'guide bars it has been found that apost-heating treatment of the composite article which results in theformation of an I 4 the joining of the wrought strip to the steelguide-bar has beenv accomplished, the tabs and the portions of wroughtstrip joined thereto are machined from the article. In this embodimentof the invention any danger of burnthrough in the steel article isavoided and a continuous high-qualitybonding between the wroughtcobalt-base alloy strip and steelbase member is ensured.

The following example is presented to illustrate the present invention.

Example 1' A inch strip, 9 inches long, was sheared from a 0.090inchisheet of cobalt-base alloy. The composition of the cobalt-basealloy sheet was as follows:

Chromium. 30. Tungsten 4.5. Molybdenum 1.5.

7 Carbon 1.6. Nickel 3.0. Iron 3.0.

- S c nv 2.0.

Manganese V 2.0. p

' Cobalt -s Balance.

essentially bainite structure in the heat-affected zone of r theguide-bar will prevent cracking in thesteel. With 1070 steel (AmericanIron ,and Steel Institute classifica-' tion) a sound composite articlefree from cracks is produced by post-heating the composite articleimmediately after re-solidification of the fused metal, 'at'atemperature of between 500 F. and 600 F. for about.90 minutes withsubsequent air-cooling to room temperature. The heatalfected zone asreferred to herein, and as commonly understood, is that portion of thesteel article whose structure has been altered by the heat of the fusionoperation. The hard-surfaced articles which have been produced by theabove method have been found to be characterized by having awear-resistant surface which isat least 40 to percent strongerthansurfaces previously provided by deposition or bead-weldingtechniques. It has also been found that the articles produced inaccordance with the present invention have at least about twice thetensile strength and twice the resistance to cracking as compared tosimilar articles manufactured by deposition or beadwelding techniques.

In a preferred form of the present invention, the steel 7 article whichis to be given a wear-resistant surfaceis provided with extensions atthe limits of the edge which is to be hard-surfaced. These extensions ortabs'are indicated as 39 in FIGURE 6; Additionally, the strip 15 ofcobaltbase alloy is pre-forrned to a correspondingshape. i Fusion of theadjoining port-ions of the strip and steel article is accomplished inthe manner previously described, begin-.v ning at one of the tabs andfinishing at the other. After;

illustrated in FIGURE 3.

of fused metal therebetween by means of a Heliarc typev meltingapparatus. The fused metal waspermitted to resolidify to provide acompositearticle. p

l The electrode employed in the melting apparatus was a solidtungstenrodof inch diameter groundto a point having an included angle ofabout,10 C.

In the joining of the cobalt-base alloy strip to the guidebar, fusion ofthe respective adjoining portions was accomplished by heating with thetungsten electrode, starting at one tab'and finishing at the other. Thevoltage applied to the electrode was 24 volts DC). and the current wasabout 135' amperes. The speed of the tungsten electrode was between 14and QO-inches per minute.

As soon as fusion and lie-solidification was complete, the compositearticle was immediately placed in a furnace at 500 F. to 600 F. andmaintained at this temperature for between 1 /2 and 2 hours. After thisperiod the composite article was removedfrom the furnace and air cooled.The hard-surfaced article thus obtained was free from cracks; and theregion'between the cobalt-base alloy strip andthe steel guide-bar wasstrong and sound in all respects. I v

From the above disclosure it can be seen that the present inventionprovides a novel and relatively simple and economical method forproviding hard-surfaced steel articles which are substantiallystronger,and which have much greaterresistance to cracking than hard-surfacedsteel articles previouslymanufactured by deposition or bead-weldingtechniques;

Whatis claimed is:

1. A process for providing a wear-resistant surface on a steel articlewhich comprises arranging wrought cobait-base alloy'rriaterial inclosely adjoining relation with g the steel article; fusing theadjoining portions of the steel article and wrought cobalt-base alloymaterial to form a rn-assof fused metal there-between consistingessentially of material derived from the fused-portions .of the cobaltibase alloy and steel article; subsequently causing the fused metal tosolidify; and post-heating the thus produced composite article to avoidcracking in the heat-affected zone of the steel portion ofthe compositearticle; said wrought cobalt-base alloy material having a composition ofbetween about 30 and 31 percent chromium, about 4.5 percent tungsten,between about 1.1 and about 1.6 percent carbon, up to 1.5 percentmolybdeum, up to 3 percent nickel, up to 3 percent iron, up to 2 percentsilicon, up to 2 percent manganese, the balance being substantially allcobalt.

2. A process for providing a wear-resistant surface on an edge of aplain carbon steel article which comprises pre-forming a strip ofwrought cobalt-base alloy material to the shape of the edge which is tobe provided with a wear-resistant surface, the strip of cobalt-basealloy having a thickness substantially the same as the edge to besurfaced; arranging said edge and said cobaltbase alloy strip in closelyadjoining relation; fusing the adjoining portions of the steel articleand cobalt-base alloy strip to form a mass of fused metal therebetweenconsisting essentially of material derived from the fused portions ofthe cobalt-base alloy and steel article; subsequently causing the fusedmetal to solidify; and post-heating the thus produced composite articleto avoid cracking in the heataifected zone of the steel portion of thecomposite article, said cobalt-base alloy strip having a composition ofbetween about 30 and 31 percent chromium, about 4.5 percent tungsten,between about 1.1 and about 1.6 percent carbon, up to 1.5 percentmolybdenum, up to 3 percent nickel, up to 3 percent iron, up to 2percent silicon, up to 2 percent manganese, the balance beingsubstantially all cobalt.

3. A process for providing a wear resistant surface on an edge of aplain carbon steel article which comprises pre-forming a strip ofwrought cobalt-base alloy material to the shape of the edge which is tobe provided with a wear-resistant surface, the strip of cobalt-basealloy having a thickness substantially the same as the edge to besurfaced; arranging said edge and said cobalt-base alloy strip inclosely adjoining relation; fusing the adjoining portions of the steelarticle and cobalt-base alloy strip to form a mass of fused metaltherebetween consisting essentially of material derived from the fusedportions of the cobalt-base alloy and steel article; subsequentlycausing the fused metal to solidify; and post-heating the thus producedcomposite article to produce an essentially bainite structure in theheat-affected zone of the steel portion of the composite article, saidcobalt-base alloy strip having a composition of between about 30 and 31percent chromium, about 4.5 percent tungsten, between about 1.1 andabout 1.6 percent carbon, up to 1.5 percent molybdenum, up to 3 percentnickel, up to 3 percent iron, up to 2 percent silicon, up to 2 percentmanganese, the balance being substantially all cobalt.

4. A process for providing a wear-resistant surface on an edge of aplain carbon steel article which comprises preforming a strip of wroughtcobalt-base alloy material to the shape of the edge which is to beprovided with a Wear-resistant surface; arranging said edge and saidcobalt-base alloy strip in closely adjoining relation; fusing theadjoining portions of the steel article and cobalt-base all-0y strip toform a mass of fused metal therebetween consisting essentially ofmaterial derived from the fused portions of the cobalt-base alloy andsteel article; subsequently causing the fused metal to solidify; andimmediately post-heating the thus produced composite article at atemperature of about 500 F. to 600 F. for about minutes with subsequentair-cooling to room temperature to thereby avoid cracking in theheat-affected zone of the steel portion of the composite article, saidcobalt-base alloy strip having a composition of between about 30 and 31percent chromium, about 4.5 percent tungsten, between about 1.1 andabout 1.6 percent carbon, up to 1.5 percent molybdeum, up to 3 percentnickel, up to .3 percent iron, up to 2 percent silicon, up to 2 percentmanganese, the balance being substantially all cobalt.

References fitted by the Examiner UNITED STATES PATENTS 1,688,360 10/28Steigerwald 29-487X 1,828,977 10/31 Miller 29-487 X 1,917,901 7/33Rohlfing 29 4s7 X 2,673,276 3/54 Allardt -t 29-487 X FOREIGN PATENTS448,683 5/48 Canada.

OTHER REFERENCES Supplement to Atlas of Isothermal TransformationDiagrams, published by United States Steel (pages 17, 18, 78, 82 and 83relied on).

WHITMORE A. WILTZ, Primary Examiner.

JOHN F. CAMPBELL, Examiner.

1. A PROCESS FOR PROVIDING A WEAR-RESISTANT SURFACE ON A STEEL ARTIC''EWHICH COMPRISES ARRANGING WROUGHT COBALT-BASE ALLOY MATERIAL IN CLOSELYADJOINING RELATION WITH THE STEEL ARTICLE; FUSING THE ADJOINING PORTIONSOF THE STEEL ARTICLE AND WROUGHT COBALT-BASE ALLOY MATERIAL TO FORM AMASS OF FUSED METAL BETWEEN CONSISTING ESSENTIALLY OF MATERIAL DERIVEDFROM THE FUSED PORTIONS OF THE COBALTBASE ALLOY AND STEEL ARTICLE:SUBSEQUENTLY CAUSING THE FUSED METAL TO SOLIDIFY; AND POST-HEATING THETHUS PRODUCED COMPOSITE ARTICLE TO AVOID CRACKING IN THE HEAT-AFFECTEDZONE OF THE STEEL PORTION OF THE COMPOSITE ARTICLE; SAID WROUGHTCOBALT-BASE ALLOY MATERIAL HAVING A COMPOSITION OF BETWEEN ABOUT 30 AND31 PERCENT CHROMIUM, ABOUT 4.5 PERCENT TUNGSTEN, BETWEEN ABOUT 1.1 ANDABOUT 1.6 PERCENT CARBON, UP TO 1.5 PERCENT MOLYBDEUM, UP TO 3 PERCENTNICKEL, UP TO 3 PERCENT IRON, UP TO 2 PERCENT SILICON, UP TO 2 PERCENTMANGANESE, THE BALANCE BEING SUBSTANTIALLY ALL COBALT.
 4. A PROCESS FORPROVIDING A WEAR-RESISTANT SURFACE ON AN EDGE OF A PLAIN CARBON STEELARTICLE WHICH COMPRISES PREFORMING A STRIP OF WROUGHT COBALT-BASE ALLOYMATERIAL TO THE SHAPE OF THE EDGE WHICH IS TO BE PROVIDED WITH AWEAR-RESISTANT SURFACE; ARRANGING SAID EDGE AND SAID COBALT-BASE ALLOYSTRIP IN CLOSELY ADJOINING RELATION; FUSING THE ADJOINING PORTIONS OFTHE STEEL ARTICLE AND COBALT-BASE ALLOY STRIP TO FORM A MASS OF FUSEDMETAL THEREBETWEEN CONSISTING ESSENTIALLY OF MATERIAL DERIVED FROM THEFUSED PORTIONS OF THE COBALT-BASE ALLOY AND STEEL ARTICLE; SUBSEQUENTLYCAUSING THE FUSED METAL TO SOLIDFY; AND IMMEDIATELY POST-HEATING THETHUS PRODUCED COMPOSITE ARTICLE AT A TEMPERATURE OF ABOUT 500*F. TO600*F. FOR ABOUT 90 MINUTES WITH SUBSEQUENT AIR-COOLING TO ROOMTEMPERATURE TO THEREBY AVOID CRACKING IN THE HEAT-AFFECTED ZONE OF THESTEEL PORTION OF THE COMPOSITE OF BETWEEN ABOUT 30 AND 31 PERCENTCHROMIUM, ABOUT 4.5 PERCENT TUNGSTEN, BETWEEN ABOUT 1.1 AND ABOUT 1.6PERCENT CARBON, UP TO 1.5 PERCENT MOLYBDEUM, UP TO 3 PERCENT NICKEL, UPTO 3 PERCENT IRON, UP TO 2 PERCENT SILICON, UP TO 2 PERCENT MANGANESE,THE BALANCED BEING SUBSTANTIALLY ALL COBALT.